1. Field of the Invention
The present invention relates to an improved head drum assembly for use in a tape recorder such as a compact size camcorder of a digital video camera (DVC).
2. Description of the Related Art
Generally, in a tape recorder such as a compact size camcorder of a digital video camera or a video cassette recorder (VCR), in order to scan magnetic tape and thus record video data thereon and/or reproduce video data therefrom, a tape recorder deck includes a head drum assembly having a magnetic head rotatable at high speed.
Referring to FIGS. 1A and 1B, a conventional head drum assembly 100 for a tape recorder includes a rotary drum 110, a stationary drum 120 and a drum cover 130. The rotary drum 110 supports a magnetic head (h), which scans a moving magnetic tape (not shown) to record/reproduce video data thereon/therefrom, and is rotatably mounted on the shaft 140. The stationary drum 120 and the drum cover 130 are press-fitted to be placed on the lower and the upper parts of the shaft 140, respectively, with the rotary drum 110 being interposed therebetween.
The drum cover 130 includes a conductive bushing member 131 in a form of a flange which is press-fitted in the shaft 140 so as to be positioned on the rotary drum 110, a cover member 132 formed by a resin molding and joined with the bushing member 131 by a pair of screws (s), and a conductive earth plate 133 supported by one of the screws (s) to be exposed through the upper surface of the cover member 132 and electrically connected to the sub circuit board 153.
Between the drum cover 130 and the rotary drum 110, a rotary transformer 152 and a stationary transformer 151 facing the rotary transformer 152 are disposed to transmit the signals recorded/reproduced on/from tape by the magnetic head (h). In order to connect the magnetic head (h) and the coil (c) of the rotary transformer 152 through soldering, a terminal 155 is preferably interconnected therebetween as a medium because direct soldering is not easy. Accordingly, in order to enable easy soldering of the coil (c) first, terminal 155 is attached to the lower part of the rotary transformer 152. Next, a hole 115 is defined in the rotary drum 110, and the upper part of the terminal pin 111 is attached to the terminal 115. Next, one end of the coil (c) is soldered to the connecting area between the terminal 155 and the terminal pin 111. As shown in FIG. 2A, the lower end of the terminal pin 111 is soldered to a fine patter coil (FPC) 117 which is disposed at the lower part of the rotary drum 110. Of course, the FPC 117 is connected to the magnetic head (h) by soldering.
To the lower part of the rotary drum 110 is provided a motor rotor 160 which has a donut-shaped magnet 162 disposed within a ring-type rotor casing 161 thereof, and to the upper part of the stationary drum 120, a motor stator 170 is mounted. The motor stator 170 is formed in a type in which the so-called FP coil (fine pattern coil) is formed into a disc pattern and disposed to face the donut-type magnet 162 to obtain a result of a more compact-sized head drum assembly 100. Such motor stator 170 usually has the three-layered structure consisting of first substrate 171, a second substrate 172 and a third substrate 17 which are stacked on one another in turn.
With regard to the motor stator 170, there is a torque generation coil pattern (A) formed on the first and second substrates 171, 172, while a frequency generation coil pattern (B) for speed control and a phase generation coil pattern (C) for phase control is formed on the third substrate 173.
As shown in FIG. 2C, the first substrate 171 is formed of a structure in which a copper membrane 171b in fine pattern is formed on an epoxy substrate 171a, i.e., on a base plate, and a protective layer 171c is formed thereon. The second and the third substrates 172 and 173 are formed in the same structure.
In the head drum assembly 100 constructed as above, the rotary drum 110 is rotated by the electro-magnetic interaction between the motor rotor 160 and the motor stator 170. As the rotary drum 110 is rotated, the magnetic head (h) mounted in the rotary drum 110 is also subsequently rotated, thereby scanning the tape and recording/reproducing data on/from the magnetic tape. The data obtained from the scanning of the magnetic head (h) is transmitted to the rotary transformer 152 and the stationary transformer 151 via the terminal pin 111 and the coil (c), and then to the camcorder system via the sub circuit board 153, which is connected to the stationary transformer 151. The data is then processed at the camcorder system. Reference numerals 140a and 140b denote bearings, and 141 an elastic member, respectively.
However, the conventional head drum assembly 100 constructed as above for use in the tape recorder is accompanied with the following drawbacks:
First, because the cover member 132 is formed of an insulating resin through a molding process, the conductive bushing member 131 and the screws (s) are required to ensure stable electric connection between the sub circuit board 153 and the earth plate 133 for a stable earthing of the head drum assembly 100.
Additionally, because the drum cover 130 requires various components such as the bushing member 131, the cover member 132, the earth plate 133, and a pair of screws (s) to connect the related parts, the number of manufacturing steps such as soldering of the earth plate 133 with respect to the sub circuit board 153, or bonding of the cover member 132 to the bushing member 131, are also increased. As a result, due to increased number of necessary parts and manufacturing steps, productivity deteriorates while the manufacturing costs increase.
Second, a significant amount of components and manufacturing steps are also required in order to connect the magnetic head (h) and the coil (c) of the rotary transformer 152. The terminal 155 has to be attached to, and the hole 115 has to be formed in, the rotary drum 110, so that the upper part of the terminal pin 111, the terminal 155 and the coils (c), can be connected through the hole 115. Then, the lower part of the terminal pin 111 is attached to the FPC 117 which is disposed at the lower part of the rotary drum 110, and the FPC 117 is connected to the magnetic head (h) by soldering.
Furthermore, because signal connection between the rotary transformer 152 and the magnetic head (h) can be achieved only after a plurality of processes, signal transmission rate is degraded, and thus performance of the product deteriorates.
Third, because the motor stator 170 is formed in the three-layered structure having the first substrate 171, the second substrate 172 and the third substrate 173, each of which are bonded to one another in turn, the number of parts and manufacturing steps increase and manufacturing costs increase. Furthermore, the copper patterning on the respective substrates also causes decreased productivity.